How is energy converted into matter?

[adam_grif]

Exactly what it says on the tin. Is there some way we can go from having energy to having mass? A long time ago I came across some kind of process by which it happened, but it required particles with rest mass for the process to work. How would you go from having a bunch of energy but no mass to having mass? Can it be done?

Additionally, does current big bang cosmology state that this happened (starting with energy only) or does it say that mass was already there in the first moments of the universe?

[Shroom Man 777]

Also, how does one lose mass by exercise? I mean, where does that fat go? I know it's metabolized for energy and stuff. But how does the mass disappear? Does it go out by sweat, by poop, or something?

[Skgoa]

If I remember my school biology correctly, you breath it out.
edit: the CO2, the water part of carbonhdyroxides is of course sweat or pissed out.

[UnderAGreySky]

I seem to recall that a gamma ray can split into a positron-electron *pair if it passes very close to a nucleus. Took long since I read about it though.

*inserted on editing

[adam_grif]

I seem to recall that a gamma ray can split into a positron-electron *pair if it passes very close to a nucleus. Took long since I read about it though.

*inserted on editing

Yeah I think that was the process I came across last time when I started googling for the answer. As previously stated, it requires matter to already be there in order to create more. It seems like there should be a way for energy to combine into matter somehow, the inverse of an matter/anti-matter reaction.

Also, how does one lose mass by exercise? I mean, where does that fat go? I know it's metabolized for energy and stuff. But how does the mass disappear? Does it go out by sweat, by poop, or something?

The mass you have in food/fat is a chemical energy store, when the energy gets used up, the now useless mass gets passed out of the body in breath, sweat, urine and feces.

[Teleros]

I seem to recall reading that you can use lasers to generate matter - the trouble of course is that you tend to get equal parts matter and antimatter, so unless you can separate the two (and deal with the antimatter somehow... is it possible to convert antimatter into ordinary matter?) you'll just end up with more photons zipping around. Of course, all this is horrendously inefficient if you're using it to build anything you can see with, say, an ordinary microscope, although I suppose if you're a sci-fi civilisation that can tap the Culture Grid and or similar it may be useful. From Wikipedia:

1. 1 electronvolt = ~1.6e-19J.
2. 1 electronvolt = ~1.8e-36kg.

I make it 8.99e16J to create 1kg of mass, assuming 100% efficiency. Half of that kilogram will of course be antimatter.


As for natural processes, the only two that I'm aware of are the big bang and black holes (the latter being related to Hawking radiation).

[Mayabird]

Shroomy is being sarcastic, mang.

Anywho, ten seconds of Googling to confirm what I was remembering and I found this link: Ask an astrophysicist at NASA. Yeah, you can do it, but it takes a hella lot of energy (so most people don't even bother) and you can't just make matter; it's matter and antimatter together and then it's a lot of effort keeping them from recombining.

[Kuroneko]

You're asking the wrong question. There is no such thing as energy in itself; energy is a property of physical systems, not something that has independent existence. In QM, elementary particles of the same type are identical--completely indistinguishable not just in practice, but in principle. Why is this so? After all, we don't have any trouble telling macroscopic objects part, even if they are of the same type. Quantum field theory provides the answer: they're identical because they're excitations in the same field.

So perhaps the question should be be: is there some way a massless field can give energy to massive field? Of course it can. For example, the electromagnetic field (with massless photons for particles) couples to a certain Dirac field (with electrons and positrons for particles), and this coupling is the source of 'electric charge'. As a result, sufficiently energetic photons can produce electron-positron pairs. And not just in the vicinity of a nucleus, although lacking that, we'd need more than one photon--sufficiently energetic light, with enough density, can naturally condense into matter.

But we can naturally ask a follow-up question: why are some fields massive, anyway? There isn't a clear answer to that question, although it has been suggested that they do so by interaction with yet another field (it has not yet been observed).

Additionally, does current big bang cosmology state that this happened (starting with energy only) or does it say that mass was already there in the first moments of the universe?

The massive fields would acquire energy from the inflaton field that drives cosmic inflation.

[Shroom Man 777]

Shroomy is being sarcastic, mang.

I wasn't!

Seriously. Sometimes it amazes me, how body loses mass and shit just by pissing/exhaling. God, the fundamental aspects/whatevers of all these biochemical metabolic processes is mindboggling.

The mass you have in food/fat is a chemical energy store, when the energy gets used up, the now useless mass gets passed out of the body in breath, sweat, urine and feces.

NO! Poop is food that didn't get absorbed! With... some additives. Urm, yeah. I guess you are correct.

Yeah, sure, urine and sweat are the result of metabolic processes with oxygen and other stuff being converted into carbon dioxide and stuff that gets peed and breathed out.

But I really find it incredible to see fat people just *work* their mass off. I mean, they don't discard their excess mass/fats by pooping out enormous quantities of crap. It all comes out of breath/pee/sweat? Amazing! Then again, most of the human body is water!

[Simon_Jester]

WARNING: Not a biochemist!
The body powers itself by burning carbon with oxygen; fat is just our way of storing burnable carbon for emergencies such as "there's nothing edible within a fifty mile radius." As in a car engine, the carbon that actually gets burnt goes to carbon dioxide; unlike in a car engine, the CO2 goes out the same lungs that serve as an oxygen intake.

So I'd expect that fat people are exhaling most of that surplus weight. Which is why it takes so freaking long.

[Darth Wong]

Additionally, does current big bang cosmology state that this happened (starting with energy only) or does it say that mass was already there in the first moments of the universe?

Naturally, Kuroneko's response is the best one. However, as an aside, I don't think there is any real distinction between mass and energy in black holes and similar phenomena. It's all just mass/energy.

[Cykeisme]

Wow this made me go look up quantum field theory.

Unfortunately I feel that without being able to grasp the math, I don't really understand anything; the best I get is a model in my head that is a very rough and inaccurate approximation of what quantum field theory describes.

That is all.

[Gil Hamilton]

WARNING: Not a biochemist!
The body powers itself by burning carbon with oxygen; fat is just our way of storing burnable carbon for emergencies such as "there's nothing edible within a fifty mile radius." As in a car engine, the carbon that actually gets burnt goes to carbon dioxide; unlike in a car engine, the CO2 goes out the same lungs that serve as an oxygen intake.

So I'd expect that fat people are exhaling most of that surplus weight. Which is why it takes so freaking long.

Well, no, this isn't how it works. CO2 is a byproduct of citric acid cycle, specifically where enzymes snip off bits of carbon chains to make the metabolite appropriate for the next stage of the cycle (they are oxidized, but it doesn't involve oxygen). Oxygen is used later as an electron acceptor, but there oxygen is reduced to water.

This is completely different than combustion. Fat people aren't exhaling their surplus weight, not directly at any rate. The reason it takes so long is fat stores ALOT of energy. A kilogram of fat contains something like 9000 kcals. That's not trivial to burn off.

[Spectre_nz]

So, pardon the tangent from the posted topic, but the divergence into metabolism caught my interest and I did a few back of the envelope calcs. I'm a chemist rather than a biochemist, but they're somewhat interchangeable.

I wasn't actually sure what kind of ballpark mass you could lose through exhalation so;

The biological demand for oxygen in the average human (say 70kgs) is around 250ml/min at rest (not sleep), and can be as much as 5 times this under heavy exertion. I'll use that assumption but obviously, actual mileage will vary with your mass and metabolism.

So, we can take a figure of 0.01117mol/min O2 consumption, rising to 0.05585 under heavy exercise. From wiki and my recollection of 3rd year, you can assume all that is coming out again as CO2 (with the O in the H2O coming from glucose) so you're looking at 0.01117mol/min CO2, converted back to grams; 0.492g/min, CO2 out for 0.357g O2 in.
Call it a ball park mass loss of 0.135g/min at rest. 8.1g an hour, or 40g/hr during heavy exertion.

Not being a biochemist, I don't know if your body excretes the H2O it gains from glucose metabolism or holds on to it, but that would be another 9.4g/hr at rest. And you can probably discount more water when you're metabolizing fat, as your body has to hold water along with fats to balance the osmolarity.

So yeah, looks like you have the potential to breath and piss out a few hundred grams a day. I have no idea if you excrete ketones and amino acids left over from fat metabolism in faeces. I know you lose a fair few red blood cells that way, so there's more mass out the door.

Well, no, this isn't how it works. CO2 is a byproduct of citric acid cycle, specifically where enzymes snip off bits of carbon chains to make the metabolite appropriate for the next stage of the cycle (they are oxidized, but it doesn't involve oxygen). Oxygen is used later as an electron acceptor, but there oxygen is reduced to water.

I have a habit of black boxing metabolism, and then it ends up looking very much like an engine. O2 goes in, stored carbon source gets oxidized, CO2 comes out. For me it’s very easy to see them as the same thing, only the scale machinery is different. It won't work for research papers, but it suffices as an approximation day to day.

[Simon_Jester]

Well, no, this isn't how it works. CO2 is a byproduct of citric acid cycle, specifically where enzymes snip off bits of carbon chains to make the metabolite appropriate for the next stage of the cycle (they are oxidized, but it doesn't involve oxygen). Oxygen is used later as an electron acceptor, but there oxygen is reduced to water.

This is completely different than combustion. Fat people aren't exhaling their surplus weight, not directly at any rate. The reason it takes so long is fat stores ALOT of energy. A kilogram of fat contains something like 9000 kcals. That's not trivial to burn off.

Ah, thank you. I sit corrected.

I have a habit of black boxing metabolism, and then it ends up looking very much like an engine. O2 goes in, stored carbon source gets oxidized, CO2 comes out. For me it’s very easy to see them as the same thing, only the scale machinery is different. It won't work for research papers, but it suffices as an approximation day to day.

This is what happened to me, only I'm an apprentice physicist, not a chemist. So I didn't think to dig and see if there was anything more subtle going on. I probably should have caught it, in hindsight.

[Gil Hamilton]

I have a habit of black boxing metabolism, and then it ends up looking very much like an engine. O2 goes in, stored carbon source gets oxidized, CO2 comes out. For me it’s very easy to see them as the same thing, only the scale machinery is different. It won't work for research papers, but it suffices as an approximation day to day.

You could encapsulate all of it as the combustion of glucose to yield water and carbon dioxide, but as a chemist myself, I would argue against it because they are tremendously different events. In this case, there is ALOT of devil in the details and adding net reactants with net products leaves out enough information that it is only partially useful, even if you can play games with the thermodynamic data from the products/reactants.

However, mostly I wanted to make Simon aware that the truth of the matter is considerably more complex than stated and that treading very carefully is needed there.

[Kanastrous]

Isn't Hawking radiation another example of mass 'appearing,' when one of a pair of virtual particles escapes a black hole's event horizon as a real particle?

[adam_grif]

Iirc Hawking Radiation results in loss of mass from the black hoke equal to the particles being created, so conservation is in effect and it's not really "mass appearing" as "mass shifting". But I ain't no expert.